MAP sensor

[BSchlossmann]

A couple of times the service engine light came on my 2004 Deville DHS. Codes were P0107 and P1107 both having to deal with the Manifold Absolute Pressure (MAP) sensor low voltage. The 3 wires to the map sensor were checked with a DVM. I had a good ground, and a good 5.0 volts. The signal line at idle was reading 1.2 volts, and as the throttle opens became less. I thought the idle voltage on the signal line should be higher, or closer to the 5 volts. With the engine off, ignition key on, I'm getting 0.0 volts on the signal line. I'm thinking that the MAP sensor needs to be replaced, but thought to first check with the members of this forum to ensure my diagnoses is correct.

The vacuum lines were checked for a leak and they appear to be in good order.

The vehicle is required to be taken in for an emissions test. Just prior to the test all codes were cleared. This caused the vehicle to be rejected for OBD readiness, a "NOT READY" was received for the evaporative control system, heated oxygen sensor and secondary air system monitors.

The week prior, the vehicle was on a road trip of over 800 miles. It ran fine, with an average of 27.2 MPG.

Does the engine have to go through several ignition cycles before the 3 monitors above respond properly as ready?

[Ranger]

Yes. They figured we'd clear the code before a test to pass so they built this readiness test in. You'll have to drive it for about a week.

[Cadillac Jim]

My 1997 FSM, page 6-243 in the table Engine 1 Data Values, lists values readable by a Tech II for "Cold Key On, Cold Idle and Hot Idle: Vehicle in PARK, A/C turned OFF..."

For the MAP, it lists two values for each condition, pressure in kPa and sensor output in Volts. For Cold Key On, it says 98 kPa, 4.67 Volts. For cold and hot idle, it lists 30 to 50 kPa, 1.50 Volts at 38 kPa. At 55 mph cruise, it gives 2.35 Volts at 55 kPa.

The MAP voltage readings seem normal, at first blush. This is a manifold air pressure reading, after all. It seems that that 4.67 Volts means no vacuum, and that 1.5 Volts is a typical or normal vacuum at idle. Your reading of 1.2 Volts is not out of line, particularly if your altitude is a few hundred feet above sea level.

[BSchlossmann]

Thanks for your response.

After reading your response over several times, I'm still a little unsure about the signal line with the engine off, key on, engine cold. I'm reading 0.0 volts, yours stated value was 4.67 volts.

The problem that I'm having is that every couple of weeks, upon cold start up, the engine will cough and sputter for a short time. At this point, increasing the RPM's for a few seconds seems to clear the problem. However, the check engine light will come on, and the two codes (P0107 & P1107) will be set.

My elevation here in Elgin, IL. is just over 800 feet above sea level, and it's good to know that the 1.2 volts on the signal line at idle isn't out of line with the expected value.

[BodybyFisher]

P0107 (from the 04 Deville manual)

Conditions for Setting the DTC

The PCM detects that the MAP sensor signal voltage is less than 0.55 volt for more than 2 seconds.

Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records

Test for an intermittent and for a poor connection at the manifold absolute pressure (MAP) sensor

From diagnostic tree, here is a good test for you, if you can retrieve the MAP parameter....

Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor. (be careful you do this correctly)

Observe the MAP sensor parameter with the scan tool.

Is the voltage more than the specified value? (4.8 volts)

Yes? Go to Step 11, Replace the MAP sensor