I have a motorhome built on a 1995 E350 chassis. when I got it, it had about 20K miles. Now it has around 30K.
The brake pedal always felt soft and mushy. The brakes always worked OK, it just didn't feel like it should feel. And the ABS light was always on.
A few years ago, I took it to the garage to have the speedometer senser replaced and it also needed the dimmer switch replaced. I asked about the ABS light and they said there is a $700 hydraulic pump somewhere in the system that isn't working. It's not supposed to be anything to worry about, more annoying than dangerous. they said the brake system would work fine, but the ABS light would always be on.
I'm wondering if the bad pump is the reason for the spongy pedal. The rear brakes were just bled after a line was replaced and it's solid fluid.
Did they reterive any trouble codes, or were they just guessing? Do you know if you have rear wheel ABS or four wheel ABS? If they knew what they were talking about, and you actually have an ABS pump, then you have four wheel ABS. If you have four wheel ABS, you need a piece of test equipment to retreive the trouble codes. To properly bleed the four wheel ABS system you also need this piece of test equipment to instruct the ABS pump to initiate a brake beeding procedure. If it is Rear Wheel ABS you can use the following procedure to retreive the codes:
----Begin procedure----
On-Board Diagnostics
Diagnostic Trouble Codes, Retrieving
NOTE: Verify the key is in the RUN position (engine does not need to be running). Next, locate the black RABS II diagnostic connector (RABS II diagnostic connector located behind trim panel at far right side of instrument panel, just below the instrument panel brace). The diagnostic connector has two mating halves (one of which has a black/orange wire connected to it). Disconnect the two halves.
Attach one end of a jumper wire to the black with orange stripe wire side of the diagnostic connector. Momentarily ground the opposite end of the jumper wire by connecting it to a good chassis ground for 1-2 seconds. Grounding this wire should start the yellow REAR ABS warning light flashing. If grounding this wire does not start the yellow REAR ABS warning light flashing, go to the Symptom Chart .
CAUTION: Care must be taken to connect only the black/orange stripe wire to ground. Connecting the mating connector wire to ground will result in a blown fuse.
The code consists of a number of short flashes and ends with a long flash. Count the short flashes and include the following long flash in the count to obtain the code number. For example, three short flashes followed by one long flash indicates diagnostic trouble Code 4. The code will continue to repeat itself until the key is turned off. It is recommended that the code be verified by reading it several times. This code will be used later for system repair instructions. It should be written down for future use. A diagnostic trouble code of 16 will be obtained when the anti-lock electronic control module detects normal system operation.
Condition / Possible Source / Action
Red Brake Warning Light Inoperative or Does Not Self-Check Open brake warning light bulb (red). Open power fuse. Open Circuit 640 (R/Y), 977 (P/W), 512 (T/LG), 531 (DG/Y), 162 (LG/R). Open resistor/diode circuit. Unseated master cylinder fluid level switch connector. Defective ignition bulb prove-out switch. GO to Pinpoint Test A .
Red Brake Warning Light Stays On When Key Is in RUN Position Ground short on Circuit 977 (P/W). Ground short on Circuit 162 (LG/R). Damaged parking brake switch. Damaged low vacuum switch (diesel only). GO to Pinpoint Test B .
Yellow Rear ABS Warning Light Does Not Self-Check Open fuse Circuit 640 (R/Y). Missing power to rear ABS warning light (open Circuit 640 [ R/Y]). Open Circuit 603 (DG). Burned out yellow REAR ABS warning light. Terminal backout in the anti-lock electronic control module harness connector at Pin 7. Harness connector not fully mated with anti-lock electronic control module. Defective anti-lock electronic control module. Open REAR ABS ground (Circuit 530 [LG/Y]). GO to Pinpoint Test C .
Yellow Rear ABS Warning Light Self-Checks but Light Automatically Begins Flashing Intermittent anti-lock electronic control module. Intermittent anti-lock electronic control module ground circuit. Intermittent yellow rear ABS warning light circuit. Blown Keep Alive Memory fuse. GO to Pinpoint Test D .
Yellow Rear ABS Warning Light Self-Checks OK, but No Diagnostic Trouble Code When Diagnostics Are Started Burned-out brake taillights. Missing anti-lock electronic control module power (Circuit 601 [ LB/PK] and associated fuse). Shorted yellow rear ABS warning light circuit (Circuit 603 [ DG]). Incorrect anti-lock electronic control module type (RABS I vs. RABS II). GO to Pinpoint Test E .
Yellow Rear ABS Warning Light Flashes Two Times When Retrieving Diagnostic Trouble Codes (Code 2) Terminal backout in the anti-lock electronic control module harness connector at Pin 13. Terminal backout in the RABS valve harness connector at Pin 1. Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection. Module or RABS valve connectors not fully mated with component. Intermittent open circuit in Circuit 599 (PK/LG). GO to Pinpoint Test F .
Yellow Rear ABS Warning Light Flashes Three Times When Retrieving Diagnostic Trouble Codes (Code 3) Terminal backout in the anti-lock electronic control module harness connector at Pin 8 or 14. Terminal backout in the RABS valve harness connector at Pin 4. Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection. Anti-lock electronic control module or RABS valve connectors not fully mated with component. Intermittent open circuit in Circuit 664 (Y/LG). GO to Pinpoint Test G .
Yellow Rear ABS Warning Light Flashes Four Times When Retrieving Diagnostic Trouble Codes (Code 4) Terminal backout in the anti-lock electronic control module harness connector at Pin 6. Terminal backout in the RABS valve harness connector at Pins 2 or 3. Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection. Anti-lock electronic control module or RABS valve connectors not fully mated with component. Intermittent open or open circuit in Circuits 535 (LB/R), or 274 (BK/W). Intermittent short or short circuit in Circuit 535 (LB/R). Defective RABS valve. GO to Pinpoint Test H .
Yellow Rear ABS Warning Light Flashes Five Times When Retrieving Diagnostic Trouble Codes (Code 5) Parking brake drag. Rear brake assembly grabby or hanging up. Connector corrosion or contamination. Intermittent open circuit in Circuit 210 (LB). GO to Pinpoint Test J .
Yellow Rear ABS Warning Light Flashes Six Times When Retrieving Diagnostic Trouble Codes (Code 6) Terminal backout in the anti-lock electronic control module harness connector at Pins 3 and 10. Terminal backout in the RABS sensor harness connector at Pins A and B. Bulkhead connector (between engine compartment and instrument panel) terminal backout or loose connection. Anti-lock electronic control module or RABS sensor connectors not fully mated with component. Intermittent open/short circuit in Circuits 519 (LG/BK) or 523 (R/PK). Damaged RABS sensor (possibly metal shavings on pole piece). Damaged RABS sensor ring (possibly teeth missing). GO to Pinpoint Test K .
Yellow Rear ABS Warning Light Flashes Seven Times When Retrieving Diagnostic Trouble Codes (Code 7) Anti-lock electronic control module fuse blown or internal open circuit. Shorted isolation solenoid internal to the RABS valve. Intermittent short or shorted circuit in Circuit 599 (PK/LG). Contamination or bent Pins 1 and 3 of RABS valve connector shorting together. GO to Pinpoint Test L .
Yellow Rear ABS Warning Light Flashes Eight Times When Retrieving Diagnostic Trouble Codes (Code 8) Anti-lock electronic control module internal fuse blown or internal open circuit. Shorted dump solenoid internal to the RABS valve. Intermittent short or shorted circuit in Circuit 664 (Y/LG). Bulkhead connector between engine compartment and instrument panel terminals shorted. GO to Pinpoint Test M .
Yellow Rear ABS Warning Light Flashes Nine Times When Retrieving Diagnostic Trouble Codes (Code 9) Terminal backout in the anti-lock electronic control module harness connector at Pin 3 or Pin 10. Terminal backout in the RABS sensor harness connector at Pins A or B. Anti-lock electronic control module or RABS sensor connectors not fully mated with component. Open or intermittent open circuits in Circuit 519 (LG/BK) or 523 (R/PK). GO to Pinpoint Test N .
Yellow Rear ABS Warning Light Flashes Ten Times When Retrieving Diagnostic Trouble Codes (Code 10) Short between anti-lock electronic control module harness connector Pin 3 and Pin 10. Short between RABS sensor connector Pins A and B. Bulkhead connector (between engine compartment and instrument panel) sensor terminals shorted together. Intermittent short circuit in Circuits 519 (LG/BK) or 523 (R/PK). GO to Pinpoint Test P .
Yellow Rear ABS Warning Light Flashes 11 Times When Retrieving Diagnostic Trouble Codes (Code 11) Terminal backout in the anti-lock electronic control module harness connector at Pin 11. Missing (burned-out) stoplamps. All stoplamps must be missing or burned out to cause a Code 11. An intermittent/continuous open in Circuit 511 (LG). This open would be between anti-lock electronic control module connector Pin 11 and the stoplight switch. Worn or damaged stoplight switch. GO to Pinpoint Test Q .
Yellow Rear ABS Warning Light Flashes 12 Times When Retrieving Diagnostic Trouble Codes (Code 12) Low master cylinder fill level. Fluid leaks in vehicle brake system. Worn or damaged master cylinder fluid level switch, or fluid level circuit shorted to ground. Master cylinder float that sticks in the bottom of brake master cylinder reservoir or does not float. Failed diode/resistor element in stoplamp circuit. Damaged ignition switch. Ground short in Circuits 512 (T/LG) or 531 (DG/Y). Damaged anti-lock electronic control module. GO to Pinpoint Test R .
Yellow Rear ABS Warning Light Flashes 13 Times When Retrieving Diagnostic Trouble Codes (Code 13) Anti-lock electronic control module is damaged. REPLACE anti-lock electronic control module. TEST DRIVE vehicle. GO to Pinpoint Test S .
Yellow Rear ABS Warning Light Flashes 16 Times When Retrieving Diagnostic Trouble Codes (Code 16) No codes stored in anti-lock electronic control module. STOP. Rear anti-lock brake system functioning properly.
Intermittent Problem Suspected Intermittent voltage to anti-lock electronic control module. Less than 11 volts to anti-lock electronic control module. Other intermittent connections to speed sensor, RABS valve, etc. GO to Pinpoint Test T .
Rear ABS and Speedometer Are Not Functioning No signal from RABS sensor. Defective RABS sensor. GO to Pinpoint Test U .
Unwarranted RABS Activity Metal chips on sensor pole piece. REFER to Pinpoint Test K , Step K7.
Gap between RABS sensor and speed sensor ring is too large (greater than
1.14mm [0.045 inches]). REFER to Pinpoint Test K , Steps K11-K12.
Missing or damaged RABS sensor ring teeth. REFER to Pinpoint Test K , Step K13.
RABS sensor/sensor ring interference (gap is too small - less than [0.127mm (0.005 inches)]. REFER to Pinpoint Test K , Step K13.
Intermittent open or shorted sensor circuit. PERFORM intermittent diagnosis for Circuits 519 (LG/BK) and anti-lock electronic control unit and RABS sensor.
Intermittent open RABS sensor circuit at intermediate connections especially bulkhead. PERFORM intermittent diagnosis for Circuit 519 (LG/BK) and 523 (R/PK) at intermediate connectors.
Intermittent open RABS sensor circuit at intermediate connections especially bulkhead. PERFORM intermittent diagnosis for Circuit 519 (LG/BK) and 523 (R/PK) at intermediate connectors.
Chafed wire insulation or pinched wire due to improper short. INSPECT wiring harness from rear axle assembly to frame side rail for chafing or rub marks.
Rear brake adjustment too tight. REFER to Section 06-00 .
Linings are "grabby." REFER to Section 06-00 .
One or Both Wheels Lock Up Damaged RABS valve reset switch. REFER to Pinpoint Test H , Steps H11 and H13.
Leaky dump valve. REFER to Pinpoint Test H , Step H12.
RABS sensor air gap too large. REFER to Pinpoint Test K , Step K11.
RABS sensor/sensor ring assembly does not produce sufficient output. REFER to Pinpoint Test K , Step K10. PERFORM intermittent diagnosis for Circuit 519 (LG/BK) and 523 (R/PK) between anti-lock electronic control unit and sensor. PERFORM intermittent diagnosis for Circuit 519 (LG/BK) and 523 (R/PK) at intermediate connectors.
Brake-related concern: Damp or contaminated rear brake shoe linings.Stuck/leaking rear wheel cylinder.Overadjusted rear brakes. REFER to Section 06-00 .
Hung-up parking brake. REFER to Section 06-00 .
Leaking rear axle seal. REFER to appropriate Section in Group 05.
Stoplamp input to anti-lock electronic control module not present. REFER to Pinpoint Test Q , Steps Q1-Q4.
Stoplamps inoperative. REFER to Section 17-01 .
Hard or Soft Brake Pedal Stuck shut isolation valve (hard). REFER to Pinpoint Test H , Step H14.
Leaky dump valve (soft). REFER to Pinpoint Test H , Step H12.
Leaky isolation valve during RABS stop (soft). REFER to Pinpoint Test J , Step J7.
Stoplight switch always on while driving. REFER to Pinpoint Test Q , Steps Q1-Q4.
Hydraulic leak in rear brake tube or rear brake hose, fitting, brake master cylinder, rear wheel cylinder, or front disc brake caliper. REFER to Section 06-00 .
Air in brake system. REFER to Section 06-00 .
Brake-related concern:Little or no vacuum boost.Stuck or inoperative rear wheel cylinder or front disc brake caliper.Pinched or crimped rear brake tube or rear brake hose. REFER to Section 06-00 .
Lack of Deceleration During Medium/Hard Brake Applications Leaky dump valve. REFER to Pinpoint Test H , Step H12.
Stuck shut isolation valve. REFER to Pinpoint Test H , Step H14.
Short/open in frame or instrument panel harness (Circuits 519 [ LG/BK] and/or 523 [R/PK]).At anti-lock electronic control unit connector (Pins 3 and 10).At RABS sensor connector.At bulkhead or other interconnection.Pinched wire or worn insulation due to improper routing.Test connector (in engine compartment). REFER to Pinpoint Test K , Steps K1-K5.
Metal chips on RABS sensor. REFER to Pinpoint Test K , Step K7.
Borderline high RABS sensor to sensor ring air gap, excessive sensor ring radial runout, damaged or missing RABS sensor ring teeth. REFER to Pinpoint Test K , Steps K11 and K12.
Hydraulic leak in brake line tubing or rear brake hose, fitting, brake master cylinder, rear wheel cylinder, or front disc brake caliper. REFER to Section 06-00 .
Air in brake system. REFER to Section 06-00 .
Brake-related concern:Little or no vacuum boost.Stuck or inoperative wheel cylinder or caliper.Pinched or crimped rear brake hose or brake line tubing.Ineffective brake shoe or pad linings. REFER to Section 06-00 .
It's not a pump - its a variable accumulator. Under normal braking the accumator pistons are all at "tdc" in their cyls. When lockup is sensed, the piston in the accumulator for that system is driven down and a check valve closed, reducing the pressure to that wheel until the wheel unlocks. The piston modulates to hold the wheel just off lockup. If the pedal is released, the fluid is allowed to return to the MC. If the accumulator piston is stuck in the lowered position it is very difficult to totally bleed the system, as some air can be trapped in the accumulator. This gives a low pedal. You WILL have normal brakes with the ABS dissabled with one caveat. MOST ABS brake systems are designed to be JUST capable of locking the wheels under normal conditions, which often translates to lower brake performance than a non-ABS equipped vehicle. I've experienced driving both ABS and Non ABS equipped vehicles, otherwise the same, and being able to lock all 4 wheels on the non ABS equipped vehicle with no problem, yet not being able to force the ABS to engage on the ABS equipped vehicle under identical conditions. Personally, I prefer non ABS brakes, but when the ABS accumulator on my van failed, I fixed it. When the brake warning light comes on I know there is a problem. If it's on all the time, the problem is not brought to my attention, and it could become dangerous.
As Ed has indicated... it is important to find out whether your motorhome is equipped with RABS or 4WABS.... the diagnostic process will differ between the two.
From what I can see, your shop is shortchanging you on their assumption of the system and what it may or may not have for concerns. And I haven't even mentioned that ABS is a safety system - ignoring it's problems rate right up with "no, we don't need life jackets" and "ground strap? why?".... but that is just me....
If yours has RABS (and ALL other mechanical items in the brake system are properly installed and functioning correctly).... one possible cause would be the RABS accumulator.... this is a smallish assembly on the frame rail tied into the rear wheel brakes only.... IIRC, 4 or 5 wires on the plug (but it has been a long time). At one end of the assembly is a hexagon cap... this can be removed, the return spring taken out and the cap reinstalled..... Pump the brakes several times through the spongy feeling and remove the cap to see if the accumulator piston has moved outwards in the bore.... If so, the valve is leaking.... Word to the wise - this is brakes we are working with and care and caution need to be exercised throughout the process.
If the van has 4WABS, the HCU/module assembly is in a difficult spot to access if the shop can't lift the van.... If they can't lift it, they shouldn't be workiing on it.... but, again, that's just me.
The truly sad part of any endeavour such as this is that a shop may or may not have the abilities and/or equipment to repair some concerns. Rather than risk losing a customer by saying we can't do that, you'll have to elsewhere.... they would much rather attempt to keep you in their customer base and blow the problem off..... after all, it's just a stinking warning light, right?
A GOOD shop would explain some of the possibilities, be able to give an estimate of diagnostic time required and, after initial diagnosis, give a detailed estimate of repair costs....
We aren't talking about "fast food burgers" here... For many, their automobile will be the biggest single "investment" they have or possibly ever will make.... The opportunities for something to go terribly wrong with one of these investments is staggering and, all too often (read the newspaper), the cost is dear....
I can only suggest finding a shop more in tune with customer needs, that will spend the time to discuss the repair of all of your vehicles with you....
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